KRANJ, Slovenia (Reuters) - The first monument to the blockchain technology that underpins crypto-currencies took center stage on Tuesday on a roundabout in Slovenia, authorities in the country's fourth largest city said.

Weighing three tonnes and with a diameter of about seven meters the circular metal sculpture was unveiled next to the courthouse in Kranj, about 30 kilometers (20 miles) north of the capital Ljubljana.

The design, featuring the 'B' symbol crossed by two vertical lines that represents both blockchain and the bitcoin currency, was chosen by popular demand.

"We asked citizens on our Facebook page to decide what to place in the new roundabout and this was one of the first ideas we received... Kranj has a lot of companies dealing with high technology," mayor Bostjan Trilar told Reuters.

The monument was paid for by two local firms that use blockchain technology, a software company 3fs and digital currency exchange Bitstamp.